WASHINGTON — A federal judge revoked Paul Manafort’s bail and sent him to jail Friday to await trial, citing new charges that Manafort had tried to influence the testimony of two of the government’s witnesses after he had been granted bail.

“You have abused the trust placed in you six months ago,” U.S. District Judge Amy Berman Jackson told Manafort. “The government motion will be granted and the defendant will be detained.”

Manafort, President Donald Trump’s former campaign chairman, had posted a $10 million bond and was under house arrest while awaiting his September trial on a host of charges, including money laundering and false statements.

But Jackson said Manafort could not remain free, even under stricter conditions, in the face of new felony charges that he had engaged in witness tampering while out on bail. “This is not middle school. I can’t take away his cellphone,” she said during the 90-minute court hearing.

“This hearing is not about politics. It is not about the conduct of the office of special counsel. It is about the defendant’s conduct,” Jackson said. “I’m concerned you seem to treat these proceedings as another marketing exercise.”

Manafort, dressed in a blue suit and red tie, was led out of the courtroom by security officers. He turned and gave a last look and wave to his wife, seated in the well of the court. She nodded back to him.

His lawyer Richard Westerling had urged the judge not to send him to jail, saying that it was not required by law, and doing so “will create more challenges for the defense, which already faces trial in two courts.”

Trump, in a tweet Friday, defended Manafort and criticized Jackson’s action against him, though he seemed to misunderstand what the judge had done.

“Wow, what a tough sentence for Paul Manafort, who has represented Ronald Reagan, Bob Dole and many other top political people and campaigns,” Trump wrote. “Didn’t know Manafort was the head of the Mob. What about Comey and Crooked Hillary and all of the others? Very unfair!”

Trump also defended Manafort in remarks to reporters outside the White House.

Manafort “has nothing to do with our campaign, but I tell you I feel a little badly about it,” Trump said. “They went back 12 years to get things that he did 12 years ago.”

Trump added that Manafort “worked for me for a very short period of time.”

Asked if he might consider pardoning former aides and advisers, Trump answered: “I don’t want to talk about that.”

In a superseding indictment filed last week, the prosecutors working for the special counsel, Robert Mueller, claimed that Manafort and a close associate, Konstantin Kilimnik, had contacted two witnesses earlier this year, hoping to persuade them to testify that Manafort had never lobbied in the United States for Viktor Yanukovych, the pro-Russia president of Ukraine.

The government alleges that Manafort violated the law by failing to report those lobbying efforts to the Justice Department and by lying to federal authorities about his activities.

The day after he was indicted in February in connection with those offenses, prosecutors claim, Manafort began trying to influence the accounts of two members of a public relations team who had worked with him, reaching out to them by phone, through encrypted messages and through Kilimnik. According to prosecutors, he tried to hide the communications by using a technique called “foldering” in which multiple people have access to the same email account and communicate by saving messages in a drafts folder rather than sending them.

Manafort’s attorneys have denied the tampering allegations and accused prosecutors of conjuring charges to pressure him to flip his plea and turn against Trump and his associates.

Manafort had been confined to his home on electronic monitoring and other restrictions since he was first indicted Oct. 27 during Mueller’s probe of Russian interference in the 2016 presidential election. Most of the criminal counts relate to activity that preceded Manafort’s time as Trump’s campaign manager, from March to August of 2016, when he resigned amid news reports that he had received secret cash payments for his Ukraine consulting.

Prosecutors had previously complained to the judge about Manafort’s behavior as he awaited trial. In December, they accused him of violating a court’s gag order by helping ghostwrite an op-ed piece defending his work in Ukraine for an English-language newspaper in Kiev.

Jackson, the judge, declined to punish Manafort then but warned she would likely consider similar actions in the future as a violation.

In asking for Manafort to be jailed, prosecutor Greg Andres said in court that there was a danger Manafort would continue to commit crimes.

“There is nothing on the record of this court that assures that Mr. Manafort will abide by conditions” of pretrial release short of jail, Andres said.

Andres said Manafort’s efforts were “not random outreaches,” but part of “a sustained campaign over a five-week period” aimed at getting the witnesses to back up a false story that he had lobbied only in Europe.

The distinction matters because unregistered foreign lobbying in the U.S. is a crime, while lobbying solely in Europe would be outside the special counsel’s jurisdiction.

Jackson said she was particularly disturbed that some of the contacts occurred after Manafort had been specifically ordered by another federal judge to avoid all contacts with witnesses involved in Mueller’s investigation or prosecution of him. That judge is overseeing a separate case in Northern Virginia, where Manafort faces additional charges of tax evasion, bank fraud and failure to report foreign bank accounts.

“I have no appetite for this,” Jackson told Manafort shortly before he was led out of the courtroom to be transported to jail. “I have struggled with this decision.”

But she said that even if she explicitly ordered Manafort never to contact any of the government’s 56 witnesses, she could not be certain he would comply. “Will he call the 57th?” she asked. She also implied that she was running out of patience with Manafort’s explanations of his behavior, saying the case “continues to be to this minute extraordinary.”

Manafort’s lawyers suggested that he had reached out innocently to his former colleagues, not knowing whether they had been contacted by Mueller’s team. But Andres said Manafort was simply deceiving the court, just as he had deceived law enforcement agencies and tax authorities over the years. “It’s inconceivable that he did not know they were potential witnesses,” he said.

Besides violating laws on disclosure of lobbying on behalf of foreign interests, the government has accused Manafort of laundering more than $30 million in income he received over a nine-year period for lobbying for Yanukovych and his political allies.

As evidence that Manafort lobbied in the United States, prosecutors submitted a four-page memo that Manafort wrote to Yanukovych detailing his campaign to convince members of Congress, the State Department and the Western news media that Yanukovych was a champion of democratic reforms. Yanukovych, who was elected president in 2010, fled to Russia in 2014.

The government alleges that the offenses are part of a complex financial conspiracy led by Manafort and aided by Rick Gates, Trump’s deputy campaign chairman, and Manafort’s right-hand man, Kilimnik, who has been linked to Russian intelligence.

Information for this article was contributed by Sharon LaFraniere of The New York Times; by Spencer S. Hsu, Ellen Nakashima and Devlin Barrett of The Washington Post; and by Chad Day and Ken Thomas of The Associated Press.